Metal chelates of oxazolidinones as central nervous system stimulants



Oct. 22, 1963 B. H. CANDON EI'AL 3,108,045 METAL CHELATES OF OXAZOLIDINONES AS CENTRAL I NERVOUS SYSTEM STIMULANTS Filed March 22, 1960 2 Sheets-Sheet 1 ORNEY Oct. 22, 1963 B. H. CANDON ETAL 3,108,045

METAL CHELATES OF OXAZOLIDINONES AS CENTRAL I NERVOUS SYSTEM STIMULANTS Flled March 22, 1960 2 Sheets-Sheet 2 WAVE NUMBERS IN CM- WAIE LENGTH lN MICRONS WAVE NUMBERS IN CM" 5 WAVE LENGTH lN MICRONS INVENTORS Basil H -cfl-MAOK No.1 Class) mfkrap Evwnifi Law ul.

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11 TTORNE Y United States Patent METAL CEELATES 0F GXAZOLIDEJONES AS CENTRAL NERVOUS SYSTEM STIMULANTS Basil H. Candon, Clifton, and Max Chessin, Fair Lawn, Ni, and Winthrop Everett Lange, Needham, Mass, assignors, by mesne assignments, to The Purdue Frederick (Zompauy, New York, N.Y., a corporation 02 New York Filed Mar. 22, 1960, Ser. No. 16,758 19 Claims. (Cl. 167-65) The present invention relates to metal chelates of 2- imino--phenyl-4-oxo oxazolidine, hereinafter referred to as pheniminooxazolidinone, also known as Z-imino-S- phenyl-4-oxazolidinone which has the structural formula:

Phenimjnooxazolidinone is recited to have certain central nervous system stimulating qualities (CNS) with low incidence of the side eilects usually attendant upon the administration of arousal amines.

The subject matter of the present invention stems from the discovery that it is possible to form certain metal chelates of pheniminooxazolidinone having an unexpected structure, which share the superior CNS stimulating characteristics of pheniminooxazolidinone but which surprisingly exhibit, among other advantages, a higher ortier of activity, an earlier onset of action, greater evenness and reliability of therapeutic action, and a broader respouse.

The metal pheniminooxazolidinone chelates were prepared by raising the pH of an aqueous or hydroalcoholic solution of pheniminooxazolidinone to 11 or more and then adding an aqueous solution of an appropriate metal salt, selected from salts of magnesium, copper and iron from which solution there is precipitated the corresponding metal chelate of pheniminooxazolidinone.

The fact that the chelates formed are N,N'-chelates, i.e. bond with the two nitrogen atoms to form a fourniembered ring, was surprising in view of the fact that from a consideration of the structure of pheniminooxazolidinone it would have been expected that the bonding would be between the number 3 nitrogen atom and the carbonyl oxygen atom. This is especially true in the case of magnesium chelates. Of course, the number of water molecules comprising the water of chelation consists of the difierence between the number of coordinate bonds of the chelated metal molecule which are otherwise filled, as by the bonding of the metal into the chelate ring, and the coordination number of the metal. Water of hydration also may be present as, for example, in the case of the magnesium chelate.

Pharmacological studies conducted with the magnesium chelate of pheniminooxazolidinone indicate that it induces CNS stimulation in monkeys, dogs, cats, rabbits, rats and mice, the duration and degree of activity depending upon the dose administered. For example, the minimal effective dose on the overt behavior on the rhesus monkey is 2.5 to 5 mg. per kg. on oral administration, while the duration of hyperactivity was from '6 to 8 hours. With increasing doses the increased locomotor activity was prolonged. Thus,'when 10 to 25 mg. per kg. were administered by mouth the duration oi" activity was extended to the range oi? 48 to 72 hours. Even with the higher dosages the absence of side effects was noted.

The oral LD in mice was determined to be approximately 1500 mgs. per kg.

A comparative acute toxicity study done in male albino rats, wherein oral doses of pheniminooxazolidmone and pheniminooxazolidinone magnesium chelate were given suspended in a 5% aqueous gum acacia solution .(administered the fasting state), employing a 4-dose assay and 10 rats per dose level, revealed the following one-week results:

PheniininooxazolidinoneLD =550 mg./kg. (stander error: 0.035; limits of error: to 117%) Magnesium chelate of pheninfino0xazolidinoneLD :550 mg/kg. (standard error: 0.035; limits of error: 85% to 117%) The above results were calculated according to Graphic Analysis method of E]. De Beer, J. Exptl. Pharmacol. &Therap. 85: 1-13 (1945).

It is notable that although the results in the LD comparative studies above undertaken are equivalent, the magnesium chelate contains approximately 70% of the pheniminooxazolidinone as active moiety and hence the studies indicate that on the basis of the amount of such active moiety the chelate is substantially more active than the original base.

To measure the onset and duration of effect of the magnesium chelate compared to the pheniminooxazolidinone, screening studies with mice, based on the response to supramaximal electroshock were undertaken.

Mice received supramaximal electroshock (alternating current) through corneal electrodes. The latency period is measured for convenience from onset of shock to onset of tonic extensor phase. It includes normally a phase of increasing limb flexon. The threshold for tonic extensor convulsions is 710 ma. The latency period between shock and the extensor component of the convulsion was recorded to the nearest 0.2 second following 20 ma. (approximately twice the threshold shock).

, After establishing that pheniminooxazolidinone and magnesium pheniminooxazolidinone significantly prolongedthe supramaximal electroshock latency period following oral administration, the drugs were administered orally to mice, generally in groups of 20. Treated groups and control groups were challenged at scheduled intervals and onset and duration of action compared. Dose for each compound was mg/kg. p.o. Analysis of data presented in Table I following (statistical analysist test for significance: P=0.05) reveals that the magnesium chelate of pheniminooxazolidinone is more rapidly effective than pheniminooxazolidinone. The onset of activity of the chelate was significant at 15 minutes while pheniminooxazolidinone was not effective at /4 or /2 hour after treatmentits significant statistical activity first appeared at one hour.

TABLE I Increase in seizure latency time Time of Elec- No. over control group troshcck Ohal- Mice Expt. lcnge after per drug in hrs. group Mg. Chelate Phenirnino- (100 mg./kg.p.o.) Phenimiuooxazolidincne oxazolidinone 10 S (significant).-. N.S. (not significant), 10 N8. 10 NS 10 N .S 1 20 S. 4 20 S. 6 10 S. 6 10 S. 8 10 10 10 N.S. 1O 10 N.S.

Norn.S-:Statistica1ly significant increase in latency seizure time. N.S.=not significant statistically (t test).

The details of electroshock seizure latency experiments may be obtained from: Seizure Latency and Antipsychotic 3 Drugs by J. E. P. Toman, G. M. Everett, and R. F. Jeans, Tranquilizing Drugs, published by American Association for the Advancement of Science, Washington, DC, 1957 ed, by Dr. Harold E. Himwich, pp. 23 to 33; and J. E. P.

4 ings were neutral to litmus, followed by a small quantity of acetone, dried and powdered. The yield was 59 g. or 90%. The magnesium chelate resulting has the following structural formula:

Toman, G. M. Everett and A. H. Smith, Jr., 1954 Experi- ,IHzO mental and Other Factors Modifying Electroshock Seizt: ures in Mice, Am. J. Physiol. 179, 680.

Clinical studies made with magnesium chelate of phen- H iminooxazolidinone confirm the chronological evidence 0 detailed above to the effect that the onset of action of the The empirical formula is C H N O MgH O. The magnesium chelate of pheniminooxazolidinone is substanmolecular weight is 252.5. tially quicker than the corresponding onset of action of Micro-analysis showed the following pheniminooxazolidinone. It establishes as well the fact Calculated for C H N O MgH O: C, 42.81; H, 3.99; that a lower dosage of the magnesium chelate provides N, 11.09; 3H O, 21.43; 2H O (coordinated), 15.70; Mg, the desired therapeutic response. In clinical studies made 9.64. Found: C, 42.0; H, 4.3; N, 9.9; 31-1 0, 2053; ZH Q, to date it has been found that the required dosage of 15.76; Mg, 10.4. magnesium chelate Was 77 t0 5%? Of that q d of phen- Total water determination using the Karl Fischer methiminooxazolidinone. This in itself is an unexpected red sult since chelates are usually less active than the com- Calculated: 3H O, 2143%. Found: 3H O, 20.53%. pounds from which they are derived. Determination of water of chelation by drying at sam- The decided advantage of the magnesium chelate over le at 250 C after first drying at 100 C. to remove the pheniminooxazolidinone is its even response which y water of hydrationcontrasted to the sometimes erratic results obtained with Calculated: 2H O, 15.70%. Found: 2H O, 15.76%. pheniminooxazolidimne- F0r p in 0116 Study The compound appears as a white, odorless amorphous eleven persons who did not respond to pheniminooxazolisubstance having a melting point greater than 300 C. dillone responded favorably T0 the magllfisium chelate The fact of chelate formation is clearly indicated during Investigators uniformly commented that in the employsynthesis by a drop in pH from 11.5 to 5 upon the addin n of h m gn i chelate as n arousal g n as 7 tion of magnesium sulfate. This shows rapid hydrogen distinguished from the employment of pheniminooxazolirelease and chelate formation. dinone, more consistent success was achieved with the Magnesium chelate is found to be practically insoluble magnesium chelate. in water and other solvents, not stable to acids but stable The uniform dosage preferred was in the range of to with respect to alkali, heat, air and light. Compared to 100 mg. with the optimum daily dosage approximately 100 pheniminooxazolidinone its characteristics are as follows:

TABLE II Solubility Solubility Oil-Water M. P., C. in H2O in KOH, Partition Reaction with Treatment with (2371191.), 5% Coefiieient m-dinitrobenzene dilute H01 and heat Pheniminooxazolidinone 256. 50 Soluble 3.2 Pink Color Converted tophenyldiketotetrahydro- Magnesium Ohclate of Phen- 70 Insolub1e.. 4. 28 No color change.-. D e r sition.

iminooxazolidmone 300.

mg. Dosages from 15 through 180 mg. were adminis- The table indicates quite clearly that a new molecule is tered with significant results. involved with substantially different characteristics. Of

In addition to administration for conditions described particular interest from the pharmaceutical point of view for heniminooxazolidinone in U.S. Patent No. 2,892,753, is the difference in oil/water partition coefficients. The it was found that the magnesium chelate had unexpected 0 procedure followed in establishing the coefficients was as utility in the treatment of narcolepsy, petit mal epilepsy, follows; barbiturate and alcoholic hangovers, and antisocial dis- Commercial oleyl alcohol (Du Pont Co., HP, 137 orders. Investigators who had worked with pheniminol42/2 mm.) was used to partition the compound b oxazolidinone remarked upon the earlier onset of action tween it and water at 25 A saturated aqueous ol of magnesium chelate of pheniminooxazolidinone. tion of each compound was prepared and readings taken The invention is further illustrated by the following exwith th spectrophotometer, T 50. 1, f a t t d amples which disclose illustrative methods of preparation aqueous solution of each compound was added an equal of the compounds useful in the present invention. volume of oleyl alcohol. The mixture was magnetically EXAMPLE 1 stirred at varying intervals for three days. A portion of 0 the water layer was then removed and filtered through Bisaquo (2-Imz'n0-5-Phenyl-4-Oxaz0Zldm0ne-N,N) Filter-Cel to remove residual droplets of oil. The con- "esillm Hydrate (Magnesium chelate of Phenimi centration of each compound in the water was then deterllovxazolidinolle) mined spectrophotometrically.

To 44 025 mole) f h i i lidi was The following oil/water partition coefficients were obadded 500 ml. of ethanol and ml. of 20% sodium mined by use ofaBeckman DU spectrophotometer attwo hydroxide solution with rapid stirring. Following com- Wavelengths: plete solution of the pheniminooxazolidinone the solution was diluted with one liter of distilled water. A solution of 250 m, 260 m 62 g. (0.25 mole) of magnesium sulfate, U.S.P., in 200 ml. of water was slowly added over a period of five minutes eni in xa olidinone 3.20 3,2 alternately along with 55 ml. of 20% sodium hydroxide Magnesium Chelate of Pheniminooxazolidmone 4. 26 4.30 to return the pH to 11. The resulting mixture was stirred for one hour, allowed to settle over night, the clear aque- It is believed that at least in part the difference in oil/ ous solution decanted and the product obtained by filtrawater partition coeflicients accounts for the increased tion. The product was washed with water until the washbiological activity of the magnesium chelate and for its earlier onset of action, since a higher oil/water partition coefficient is usually taken to indicate greater and more rapid cell penetration.

Illustrative of other magnesium salts which may be employed in lieu of magnesium sulfate are the following: magnesium bromide, magnesium chloride, magnesium citrate, magnesium nitrate, magnesium acetate and magnesium phosphate.

FIG. 1 is a tracing of the infrared absorption curve of the magnesium chelate (0.3% in KBr).

FIG. 2 shows a similar tracing for pheniminooxazolidinone.

The spectra clearly show the difference in the two molecules and evidence as well the site of chelation. The two spectra are essentially the same except for the efiects shown by chelation. The carbonyl band at 1720 cm. and the i NH (amide) at 3000 cm." are not changed in the magnesium chelate. There is present in FIG. 1 a weak absorption bandat 660 cm." which may be assigned to metal donor vibrations. The slight increase in absorption in the 1500 cm. region shown in FIG. 1 indicates coordination at the C=N position. The strong absorption band at 3600 cm. may be assigned to water of coordination.

Significantly, the five-membered ring of the pheniminooxazolidinone is not altered by the formation of the magnesium chclate. It is believed that this ring in unaltered form is necessary to the biological action of both components.

EXAMPLE 2 Bisaqmr(2-lmino-5-Phenyl-4-Oxaz lidin0ne-N,N')- Copper (II (Copper Chelate of Pheniminoox'azolidinone) To a solution of 0.9 gm. (0.005 mole) of phenirninooxazolidinone in water or a waterzalcohol mixture at a pH of 11 was added 0.65" gm. (0.005 mole) of CuCl in a small quantity of water. An immediate drop in pH was noted (indicating chelate formation) and brought back to with dilute NaOH. The fact of chelation is dramatically evidenced during synthesis by the marked color change from colorless to blue. Stirring was continued for one hour, followed by filtration of the blue prepicitate. The product was washed with water, acetone and then dried. The yield was 92% based on the proposed structure. The copper chelate resulting has the following structural formula:

@t/ H t Trisaquo (Z-Imino-S-Phenyl-4-Oxaz0lidinone-N,N')Jron (III) Hydroxide. (Iron Chelate of IIteniminooxazolidinone) Iron ohelate of pheniminooxazolidinone is prepared in the same manner as copper chelate of pheniminooxazolidinone, as described in Example 11, except that ferric sulfate is substituted for copper chloride. The yield was 92% based on the proposed structure. The iron chelate resulting has the following structural formula:

The empirical formula is C H N O Fe, the molecular weight 301.0.

Micro-analysis showed the following- Calculated for C H N O Fe: C, 35.91; H, 4.35; N, 9.31; Fe, 18.55. Found: C, 35.5; H, 3.9; N, 8.9; Fe, 19.2.

The iron chelate is an amorphous light brown, odorless compound, decomposing above 200, very slightly soluble in water and other solvents, not stable to acids but stable to alkali, heat below 200, air and light.

As in the case of the magnesium chelate and the copper chelate, other iron salts may be substituted for the ferric sulfate used above.

The examples which follow illustrate the prepartion of pharmaceutical compositions according to the present invention without, however, being limited thereto.

EXAMPLE 4 Tablets 12.5 gms. of the magnesium chelate of pheniminooxazolidino-ne, 28.4 gms. of lactose, and 8.2 gms. of starch are mixed for 30 minutes. The mixture is granulated with a solution containing 0.4 gm. of gelatin in 11 mls. o-f demineralized water and 0.25 gm. of silicon emulsion. The granulate is broken up, dried at 50 C., and mixed for 10 minutes. 0.5 gm. of amylopectin is added and the mixture compressed into tablets. With a loss on drying of 0.25 gm., the yield is approximately 490 tablets, each weighing 100 mg and containing 25 mg. of the drug.

EXAMPLE 5 Capsules 12.5 gms. of the magnesium chelate of pheniminooxazolidinone is triturated intimately with 42.5 gms. of lactose. The resultant mixture is packed into the base of hard gelatin capsules (#5) and the cap closed securely. The yield is approximately 500 capsules, each weighing 110 mg. and containing 2.5 mg. of the drug.

EXAMPLE 6 S uppositories (a) 22.5 gms. of the magnesium chelate of pheniminooxazolidinone is alevigated with 300 mg. of polyethylene glycol (1500').

(b) 500 gms. of polyethylene glycol (6000) is melted and 200 gms. of polyethylene glycol (400) added to it.

(a) and (b) are combined with stirring and the resultant mixture is poured into molds and allowed to cool.

- The yield is approximately 450 suppositories, each weighing approximately 2.2 gms. and containing 50 mg. of the drug.

EXAMPLE 7 Suspension 5.0 gms. of the finely powdered magnesium chelate of pheniminooxazoliidinone is triturated with a few mls. of syrup, U.S.P. (modified with coloring, flavoring and preserving agents) The mixture is diluted gradually to 1000 mls. Each teaspoonful (5 mls.) of the suspension contains 25 mg. of the drug.

In the above examples of pharmaceutical preparations the unit dosage has been set at 25 mg. It has been found that this is an ideal and flexible unit dosage of active material, although, as brought out above, unit dosages of from 15 through 200 mg. have been found to be effective.

7 EXAMPLE 8 For the magnesium chelate of pheniminooxazolidinone in Examples 4 through 7 there may be substituted the copper and iron chelates of phenirninooxazolidinone, the

'quantity being varied in accordance with standard compounding practices to produce unit dosage forms containing 25 mg. of the drug.

It is not desired to be limited except as set forth in the following claims, the above description being by way of illustration of the invention.

What is claimed is:

1. A metal chelate of 2-imino-5-phenyl-4-oxazolidinone selected from the group consisting of 2-imino-5-phenyl-4- oxazolidinone-N,N'-magnesium, 2-imino-5-phenyl-4-oxazolidinone-N,N-copper and 2-imino-5-phenyl-4-oxazolidinone-N,N-iron.

2. Z-imino--phenyl-4-ox-azolidinone-N,N-magnesium.

3. 2-imino-5-phenyl-4-oXazolidinone-N,N-copper.

4. 2-imino-5-phenyl-4-oXaZolidinone-N,N-iron.

5. The method of preparing a metal chelate of 2- imino-5-pl1cnyl-4-oxazolidinone selected from the group consisting of the 2-imino-5-phenyl-4-oxazolidinone-N,N- magnesium, Z-imino-S-phenyl-4-oxazolidinone-N,N-copper and 2-imino 5 phenyl-4-oxazolidinone-N,N'-iron which comprises the steps of elevating a solution of 2- imino-5-phenyl-4-oxazolidinone to at least a pH of 11, introducing into the solution a salt selected from the group consisting of the salts of magnesium copper and iron and recovery from the resultant reaction mixture the said chelate.

6. The method of preparing 2-imino-5-phenyl-4-oxazolidinone-N,N-magnesium which comprises adding to a solution of 2-imino-5-phenyl-4-oxazolidinone elevated to a pH of at least 11, a magnesium salt and recovering from the resultant mixture, the white precipitate therefrom.

7. The method of preparing 2-imino-5-phenyl-4-oxazolidinone-N,N'-copper which comprises adding to a solution of 2-imino-5-phenyl-4-oxazolidinone elevated to a pH of at least 11, a copper salt and recovering from the resultant mixture, the blue precipitate therefrom.

8. The method of preparing 2-imino-5-phenyl-4-oxazolidinone-N,N'-ir0n which comprises adding to a solution of 2-imino-5-phenyl-4-oxazolidinone elevated for a pH of at least 11, an iron salt and recovering from the resultant mixture the brown precipitate therefrom.

9. A pharmaceutical composition in dosage unit form including a pharmaceutical carrier and from to 200 mg. of a metal chelate of 2-imino-5-phenyl-4-oxazolidinone selected from the group consisting of 2-imino-5-phenyl-4- oxazolidinone-N,N-magnesium, 2-imino-5-phenyl-4-oxa- 8 zolidinone-N,N'-copper and 2-imino-5-phenyl-4-oxazolidinone-N,N'-iron.

10. A pharmaceutical composition as described in claim 9, said carrier being a solid carrier.

11. A pharmaceutical composition as described in claim 9, said carrier being a liquid carrier.

12. A pharmaceutical composition as described in claim 9, said carrier being a suppository base.

13. A pharmaceutical composition in dosage unit form comprising a pharmaceutical carrier and from 15 to 200 mg. of 2-imino-5phenyl-4-oxazolidinone-N,N-magnesium.

14. A pharmaceutical composition in dosage unit form comprising a pharmaceutical carrier and from 15 to 200 mg. of Z-imino-5-phenyl-4-oxazolidin0ne-N,N'-copper.

15. A pharmaceutical composition in dosage unit form comprising a pharmaceutical carrier and from 15 to 200 mg. of 2-imino-5-phenyl-4-oxazolidinone-N,N-iron.

16. The method of stimulating the central nervous system in animals and human beings which comprises administering to the subject to be so stimulated a metal chelate of 2-imino-5-phenyl-4-oxazolidinone selected from the group consisting of Z-imino-5-phenyl-4-oxazolidinone- N,N'-magnesium, 2-imino-5-phenyl-4-0Xazolidinone-N,N'- copper and 2-imino-5-phenyl-4-oxazolidinone-N,N-iron.

17. The method of stimulating the central nervous system in animals and human beings which comprises administering 2-imino-5-phenyl-4-oxazolidinone-N,N-magnesium to the subject to be so stimulated.

18. The method of stimulating the central nervous system in animals and human beings which comprises administering 2 imino-5-phenyl-4-oxazolidinone-ll,N'-copper to the subject to be so stimulated.

19. The method of stimulating the central nervous system in animals and human beings which comprises administering 2 imino-5-phenyl-4-oxaZolidinone-N,N'-iron to the subject to be so stimulated.

References Cited in the file of this patent UNITED STATES PATENTS 2,854,379 Fancher Sept. 30, 1958 2,872,374 Beiler et al. Feb. 3, 1959 2,892,753 Schmidt June 20, 1959 2,918,483 Varul Dec. 22, 1959 2,928,856 Harwood et al Mar. 15. 1960 OTHER REFERENCES Traube: Ber. 46, 2, p. 2082, 1913. Schmidt: Chem. Abs. 50, p. 17196('b), 1956. Lienert: Chem. Abs. 51, p. 15805(e), 1957. 

16. THE METHOD OF STIMULATING THE CENTRAL NERVOUS SYSTEM IN ANIMALS AND HUMAN BEINGS WHICH COMPRISES ADMINISTERING TO THE SUBJECT TO BE SO STIMULATED A METAL CHELATE OF 2-IMINO-5-PHENYL-4-OXAZOLIDINONE SELECTED FROM THE GROUP CONSISTING OF 2-IMINO-5-PHENYL-4-OXAZOLIDINONEN,N''-MAGNESIUM, 2-IMINO-5-PHENYL-4-OXAZOLIDINONE-N,N''COPPER AND 2-IMINO-5-PHENYL-4-OXAZOLIDINONE-N,N''-IRON. 